The present disclosure relates to an optical scanning device that radiates heat inside the device and an image forming apparatus provided with the same.
An electrophotographic image forming apparatus is provided with an optical scanning device that exposes a photoreceptor by irradiating the photoreceptor with light. The optical scanning device includes a light source such as laser light, a polygon mirror that reflects light from the light source, a motor that rotates the polygon mirror, an fθ lens that forms an image of the light from the polygon mirror on a photoreceptor, and a reflective mirror that reflects the light having passed through the fθ lens toward the photoreceptor. In such an optical scanning device, each component is housed in a highly air-tight casing in order to keep out dust.
When the casing is highly air-tight, heat from a component housed inside, especially the motor or a driver of the motor, is not easily radiated and the temperature inside the casing rises. When the temperature inside the casing is high, the polygon mirror and the reflective mirror are distorted. Accordingly, a phenomenon of scanning line curvature occurs, in which the light scanned by the polygon mirror is curved. To solve drawbacks described above, various technical measures have been conventionally made to the casing so that the heat inside the optical scanning device is efficiently radiated. For example, an exposure device in which a polygon mirror and a motor are housed by an inner casing that is further covered by an outer casing is reported. In addition, an optical writing device is reported, which includes a casing with an opening, cooling fan provided inside and lid that uncovers the opening by a force applied by an air flow generated by the cooling fan in operation and covers the opening by its own weight while the cooling fan is not in operation.
However, since the inner casing is shielded from outside by the outer casing in the exposure device described above, an inner space of the outer casing provides a heat insulating effect to the inner casing. Accordingly, it may not be possible to directly radiate heat from the inner casing. In addition, since the opening is provided to the casing in the optical writing device described above, dust cannot be completely prevented from entering the device through the opening. More specifically, as the cooling fan stops and the air flow ceases, the lid rotationally moves to a direction to cover the opening. At this moment, rotational movement of the lid member generates an inward air flow that may bring fine dust into the device through the opening. Furthermore, since the optical writing device requires two driving units, one motor for the polygon mirror and another for the cooling fan, additional steps for assembling the cooling fan and wiring are required, thereby increasing manufacturing costs. Moreover, since it is necessary that the casing is configured to enable two driving units to be fixed and vibrations caused by the driving units to be suppressed, the configuration of the device will be complex.
The present disclosure has been made in view of the abovementioned situation. It provides an optical scanning device and an image forming apparatus provided therewith. The optical scanning device enables efficient cooling of a driving unit of a polygon mirror by circulating inside air by a simple configuration without a driving unit such as a cooling fan.